Thermostatic circuit interrupter



Feb. 27, 1940. L. SCHMIDT THERMOSTATIC CIRCUIT INTERRUPTER Filed March19, 1957 6 Sheets-Sheet 1 zo@ Y $113,

Feb. 27, 1940. l.. scHMlDT 2,191,501

THERMosTATIc CIRCUIT INTERRUPTER Filed Mrh 19, 19:57 s sheets-sheet 2WWW ZZ 4.Il 1

l INVENTOR.

an ATTORNEYS Feb. 27, 1940. SCHMIDT THERMOSTATIC CIRCUIT INTERRUPTER 6Sheets-Sheet 5 Filed March 19, 1937 IIIIII @Maw f i@ We ATTORNEYS Feb.27, 1940. L. SCHMIDT THERMOSTATIC CIRCUIT INTERRUPTER 6 Sheets-Sheet 4lum' 'Irl

Filed March 19, 1937 //Yff/IL IN VENTOR.

ATTORNEYJ` Feb. 27, 1940. L. SCHMIDT 2,191,501

THERMOSTATI C CIRCUIT INTERRUPTER.

Filed March 19, 1937 6 Sheets-Sheet 5 Iiil 752723 (ppmm, l ya( /WwATyT-(SIEYS Feb. 27, 1940. L. scHMxDT 2,191,501

THERMOSTATIC CIRCUIT INTERRUPTER 205 f 2161?@ e] Z3 i9 225 202 205 20ggi/ 226 E40 24j 239 ya p 22a INV /IM ATTORNE s Patented Feb., 27, 1940UNITED STATES PATENT OFFICE 2,191,501 THERMOSTATIC CIRCUIT INTERRUPTERLambert Schmidt, Leeds, N. Y.

Application March 19, 1937,v Serial No. 131,822

15 Claims. (Cl. 20G- 116) This invention relates to improvements inengage in ordinary outlet sockets and also to means for and methods ofinterrupting current incorporate socket means to be engaged by the ilowand more particularly to improvements in contact prongs of a two-prongplug.

circuit breakers of a character capable of being In carrying out theforegoing and other objects substituted for fuse plugs or cartridgefuses of of the invention, use is made of a principle in 5 the types nowin general use. circuit breakers wherein two moving arms are An objectof the present invention is to pro-A so mounted and actuated as to bemoved simulvide a circuit breaker of such character that the taneouslyaway fromV an intermediate conducting same can be substituted for fusesof various types member which becomes in effect a barrier bel0 now inuse without causing changes in receptacle tween the moving contacts oncethese contacts 10 equipment, such as cut-outs or cut-out boxes. havebeen moved out of barrier-engaging posi- Another object of the inventionisfto provide tion. Due to this arrangement of moving cona circuitbreaker of a type wherein the same can tacts and intermediate conductbarrier it hasx be reset an indefinite number of times. been found inpractice that destructive arcing is Another object is to provide acircuit breaker substantially eliminated. It is essential however 15 ofsuch construction that arcing is substantially that the moving contactsbe so actuated as to eliminated. be moved away from this barrier at thesame A further object of the invention is to provide instant andpreferably at the same rate of mocircuit breaker construction in whichmeans are tion. Should one contact leave its barrier enincorporated forinterrupting the flow of current gaging position ahead of theI other theresult without the creation of` any substantial destrucwould be toestablish an arcbetween the barrier tive arcing. and the contact rstmoving out of engagement An additional object of the invention is toprotherewith. Accordingly to insure that such de vide a circuit breakerconstruction utilizing a sired movement will be accomplished means arestationary conducting member between moving provided, in a circuitbreaker incorporating the 25 contacts, which conducting member Servesonly present invention; for mechanically moving the as a conductor andis not otherwise included in contacts out of engagement with the barrierat the circuit. the same time and at the same rate of motion.

A still further object of the invention'y is to For this purpose ashutter of insulating material provide a circuit breaker' constructionwherein is slidably mounted on the barrier bar, such shut- 30 Vthemoving contacts are actuated to move simulter being held out ofengagement with the contaneously away from the opposite sides of anintactsv during the time an uninterrupted flow of termediate ,conductingmember so that any tendcurrent is desired, or during the time the'current ency to set up destructive arcing is substantially flow iswithin the proper limits. The locking deeliminated. vice for holding theshutter in such position can 35 A further object of the invention is toprovide be released by a thermostatic bi-metal trip of a circuit breakerof the foregoing kcharacter a `character designed to operate on anoverload mounted within` a housing of such size and shape ofpredetermined value. When the trip has been that the complete unit canbe inserted in conven- Yoperated to release the shutter, the shutter is40 tional types of plug fuse cut-outs without alteraadvanced along thebarrier bar into a position 40 tion. wherein parts of the shutter areinterposed be- As another objectr` of the invention the con- 1 tween thebarrier bar and the contacts on opstruction of the circuit breaker issuch that the posite sides thereof. The shutter is so shaped same can beincorporated in a housing of comas to engage the contacts simultaneouslyand as parable size and shape to the housing of the conto move thesecontacts away from the barrier 45 ventional types of. cartridge fuses.bar at a uniform rate of movement.

A still further object of the invention is to In addition provision iSmade, through the provide a circuit breaker construction of such agencyoi insulating members, for forming chamcharacter as is capable ofbeingused as a branch bers, in conjunction with the shutter, in whichcircuit breaker whereby the same can be inchambers the movable contactterminals are serted in any suitable line to protect a singleelecisolated When they 113V@ been moved t0 Circuittrical appliance or apluralityof appliances in interrupting positions. The primary shutter isthe same line. constructed to move with great rapidity, thereby Anadditional object of the invention is to proquickly completing theformation of such chamvide a circuit breaker construction adapted tobers. Also 'the rapid movement of this shutter, 55

- ly the time in which destructive arcing can ocadvantage inherent inthis type of device resides in the speed at which a circuit can bebroken, due to the rapid movement of the shutter and also to themovement of the contact terminals in opposite directions, therebyincreasing the distance between such terminals at approximately doublethe speed possible with a breaker having only a single moving terminal.Consequentcur is materially reduced.

In one form of the invention the circuit breaker is mounted within ahousing, a part of which is of such size and shape as to fit in ordinaryscrew socket cut-outs. The housing for the circuit breaker is made ofsome suitable insulating material preferably an insulating material ofany desired composition such as a phenol condensation product. Othermaterials however, can be used. In the preferred construction the movingcontacts are normally held out of engagement with the intermediatebarrier bar until the unit hasbeen inserted in a cut-out. At such timeone of the terminals for the mechanism within the casing is moved insuch fashion that the contacts are brought into engagement with thebarrier bar thereby completing the electricaly circuit through thesecontacts and through the thermostatic bi-xnetal trip for the shutter.The mechanism of the circuit breaker is so arranged that after the unitopens the circuit due to short circuit or overload, the operating partsthereof are automatically restored L.to normal position upon removal ofthe unit from a cut-out. As a result the device is capable of indefiniteuse.

Since it is desirable in some instances that a single appliance beindividually protected by some current interrupting device, the presentinvention lends itself admirably to such practice in that a circuitbreaker within this invention is constructed as before brieflydescribed, with the exception that two socket members are mounted withinthe housing in such fashion as to be capable of receiving the contactprongs of, a plug. The housingmay be of such size and shape as to t inan ordinary screw socket or if desired the terminals for the device maybein the form of plug prongs adapted to be received by an ordinary plugsocket. In the latter construction, preferably, one of the prongs ismounted for movement and has an arm engaging the barrier bar operatingmechanism whereby the operatingv parts of the circuit breaker can bereset by removal `of the unit from its receptacle. In this manner anyappliance can be separately protected.

In a'still further form of the invention a circuit breakerlhaving-mechanism as before described is mounted within a cylindricalhousing of size and shape corresponding to the size and shape ofordinary cartridge fuses. In this construction contact caps are providedat each end of the cylinder. One of such caps is capable of axialmovement so that the operating'parts of the circuit breakerfcan be resetafter the device has operated to interrupt current flow, such resettingbeing accomplished by merely removing the unit from the clips engagingthe caps.

Other features, objects and advantages of the invention will becomeapparent by referenceto the following detailed description of thedrawings illustrating the same, wherein:

Fig. 1 is a plan view of a device embodying the invention in one formthereof and showing a telltale in one position; N

Fig. 2 is a similar view of the same device and showing the telltale inanother position;

Fig. 3 is a section taken substantially on the line 3-3 of Fig. 1; y

Fig. 4 is a side elevation with the housing partially broken away toillustrate the mechanism for operating the telltale;

Fig. 5 is a section taken substantially on the line 5 5 0f Fig. 3;

Fig. 6 is a section taken substantially on the line 6 6 of Fig. 3;

Fig. 7 is a section similar to that of Fig. 3

showing the operating parts in circuit-closing` Fig. 12 is a sectiontaken substantially on the line I2-I2 of Fig. y11;

' Fig. 13 is a section taken substantially on the line I3-I3 of Fig. 12;

Fig. 14 is a section taken substantially on the line I4-I4 of Fig. 12;

Fig. 15 is an axial section of a circuit breaker embodying the inventionand mounted within va housing adapted to replace cartridge fuses:

Fig. 16 is a similar section showing the operating parts in a diierentposition;

Fig. 17 is a section taken substantially on the line I'I-I'I of Fig. 16;

Fig. 18 is a fragmentary vertical section of a modified form of triparrangement for releasing the primary shutter; and

Fig. 19 is a section taken substantially on the line lil-I9 of Fig. 18.L

Referring now to the drawings and more particularly to Figs. 1 to V`i9,I0 indicates generally a housing within which the operating parts oi'the circuit breaker are mounted. 'I'his housing is of generallycylindrical stepped form, being made up of/a' part II, the periphery ofwhich .is shaped to accommodate .a metallic shell I2.

'I'his shell I2 is of form to be engaged in a screw threaded'v socketsuch as is commonly used in cut-out blocks. The device however,obviously can be engaged in any electrical socket `of conventional sizeand shape. The part II has a body portion I4 to which is secured a cappart I5 in some suitable fashion as shown. These parts are in screwthread engagement but it will be apparent that the parts can be securedtogether in any other suitable fashion or in fact the parts I'I and I5may be made integral if desired; in which case the top .part I6 of thecap I5 could be made separate from the cylindrical portion tlrere'offand could be secured thereto in' some suitable means. Since the shell l2serves as one terminal for the circuit breaker, an electrical connectiontherewith to other parts of the device is provided by means of a metalconducting strap Il, one end of which is in con- 75 tact with the shell;such strap passing upwardly through the flange i4 and then along the topsurface lll of this iiange to a post |8 secured 'to the ange in somesuitable fashion.

One end oi a spring contact member 29 is also secured to the surface i4by means of the post it. The member 2u has an upwardly bent portion 2l,a downward expanse 22, a lower bent portion and an upward cam surfaceexpanse E secured to a contact terminal member 2t. Since the part 2li ofthis spring and the strap lll are both held in place by the post i9 itfollows that they are electrically connected. Diametrically opposite thepost i8 is a similar post 2@ which serves to hold in place the endportion or a spring contact member, which contact member, indicatedgenerally at 29, is similar in construction to the spring memberpreviously described. This member 29 also has a contact part similar tothe part llt. In addition to the end of the member 2d the post 2S alsosecures in place one end of an arcuate shaped strap 3l; the other end ofwhich is secured in place by a post Spaced a slight distance from post32E is a similar' post This post serves to hold locked to the surfacelll a ,conducting strap which has a continuation part 35 (Fig. 6)extending downward alongside the inner wall or the part ll of thehousing, and an end part 3@ held to surface il of the bottom of part lllby a screw 3l'. lThe end 3@ is thereby secured also to an arcuate shapedstrap .tti which extends around the surface ll to a point substantiallydiametrically opposite the screw 3l? at which point a second screw 38serves to fasten the strap in the shell. A pair of substantially Zshaped conductors 40 have openings therein for the passage of screws 3land 38 whereby these two conductors are electrically connected, both tothe end part 3S and to the strap 33. rlhese conductors dll extenddownward'along the wall of a well part 4l in the member il across thebottom 42 thereof and downward alongside the opposite walls 44 of anopening in the actual bottom of the housing. The purpose of theseconductors will be explained later.

A substantially `U-shaped thermostatic bimetal trip member 45 has thelegs thereof bent at right angles to the body thereof with these legssecured to the tops of the two posts 32 and 33. Secured to the surfaceby means of a screw 46 is one end of a latch carrier 4l. The top of thislatch carrier is provided with an offset latch 48 and with an upstandingextension 49. The looped end of the U-shaped member 45 extendsdownwardly within the housing a distance sufficient to cause it toengage the upstanding part 49.

A bar 50 extends upwardly through the opening in the bottom of thehousing in such close contact with the ends of the member 40 as to makegood electrical connections therewith. The part 50 is of relativelyshort length terminating in a molded block 5| of some suitableinsulating material. Also molded in this member 5| but in insulatedrelationship to the bar 50 -is a second bar 52, a portion of which isadapted to serve as an intermediate barrier conducting bar. By means ofthis insulating connector 5| the two bars 50 and 52 are joined forsimultaneous movement as desiredf A button 54 can be secured to the endof the bar 50 to serve as a good terminal therefor.

The bar 52 is provided with a recess 55, the bottom of which is inregister with the top of the connector 5|. Extending upwardly in therecess- 55 is a stud 56 formed integrally with 'the bar. Slidably on thebar 52 is a primary shutter made up of barrier side walls and 6| andcrosswalls 62 and B4. The crosswalls 62 and 64 have relatively thin topparts extending into dome-like portions 65 and 96 respectively. Thelower parts of the dome-like portions 65 and 66 are hollowed out to forma cavity indicated generally at 61, in which cavity is positioned acoiled spring 68 one end of which rests on the top of the connector 5land the other end of which rests against the top surface of the cavity6l'. This spring B8 normally forces the entire primary shutter upwardlyto the position shown in Figs. 3, 9 and l0.

Secured to the top of the bar 52 is a secondary shutter indicatedgenerally at "lo, which shutter has a substantially circular top lll,sloping siden walls 'i2 and 'i3 and inclosing endwalls l and i5. rl'hissecondary shutter il] has a through opening rectangular in cross-sectionfor the reception of a reduced end part llt of the bar 52. The top lllof the shutter iii can be dished slightly and is positioned to have theorifice therein in an alignment with the axis of the part lt. A screw i8has the shank thereof in threaded engagementv inl an aperture of thepart 'lli to thereby lock the secondary shutter directly to the end ofbar 52.

Secured to the tops of the two posts i8 and 2S is a hooded member t8 ofgeneral U-shape in cross-section, such member having sidewalls 8l and atop 82. Screws 84 pass through the top 82 into threaded openings in theposts i8 and 28. Depending from the top 82 are arcuate shaped walls 85which in conjunction with the sidewalls 82 provide a cavity 8G which iscircular in crosssection for the reception of the secondary shutter l.Conical spring 8l is positioned in this cavity with one end thereofresting on the insulating block on the top of screw 19 and the other endseated against the top of the cavity 86. Since this spring is ofgenerally conical shape, it follows that the same can be compressedsubstantially into the form shown in Fig. 8, when the secondary shutter10 is forced into the cavity 86.

The primary shutter, the secondary shutter and the hood previouslydescribed are constructed of some suitable insulating material, such asporcelain, any suitable ceramic material or any other material of a likeor kindred character.

The wall 6| of the primary shutter has an extension provided with a flattop and with a' sloping edge which extension forms in effect a lug to beengaged by the latch 48. The wall 60 of the primary shutter is providedwith an enlargement 9| in which is cut a diagonal slot 92 (Fig. 4). Atelltale device 94 of U-shape in cross-section and of metal or any othersuitable material is slidably mounted on the top of the hood 88. Thistelltale 94 has a slot 95 therein as shown in Fig. 4. A standard 96 issecured by a screw 91 to the surface I4 and a lever 98 is pivotallysecured to such standard by a headed pin 99. A roller |00 is secured toone end of the lever 98 in position to ride in the diagonal slot 92while a second roller |0| is secured to the other end of the lever 98 toride in the slot 95. Due to this arrangement vertical movement of theprimary shutter causes revciprocation of the telltale along the hood 80.A

Vtargets will be explained later.

The operationahd use of the device just described is substantially -asfollows: the relative position of the various parts of the device priorwalls 'I2 and 'I3 of the secondary shutter are interposed between theterminals 26 and 30 on the spring contact members and at the same timeas Shown in Fig. 8 the lug 90 on the sidewall 6I of the primary shutteris engaged by the latch 48.

When it is desired to make use of the device, the housing may be screwedinto an ordinary cut-out in the same manner as is followed in the use ofconventional types of fuse plugs. As the housing is screwed into acut-out socket the button 54 on the end of the bar 50 engages the centerterminal of the cut-out socket before the device has become completelyinserted in the cutout, and consequently full insertionof the housinginto the cut-out forces the bar 50 inwardly relative to the housing, orin other words causes the parts to assume the positions shown in Figs. 7and 8. Since the bar 50 is a component part of a composite bar includingalso the bar 52, the connector 5I and the secondary shutter l0, itfollows that all of these parts are moved upwardly until the spring 68and the spring 81 become compressed. Since the lug is in engagement withthe latch 48 it follows that the primary shutter does not move upwardlyand consequently the spring 68 does become compressed. Due to thisupward movement of the secondary shutter 'I0 the terminals 26 and 30 arefree to move inwardly due to spring tension with the part I|0 of the bar52. As the secondary shutter l0 nears the end of its upward movement theterminals 26 and 30 snap into contact with portion I 0 of bar 52 withgreat' rapidity. The parts 50 and 52 of the composite bar are made ofsome good electric conducting material so that under suitable conditionscurrent is free to flow from one of the terminals of the pair 26-30 tothe other thereof through this barrier bar portion I I0.

When the parts of the device are in the condition shown in Figs. 7 and 8and are located in a cut-out, the electric circuit established therebymay betraced substantially as follows: from the conducting shell I2through the strap I1 to post I8 thence to the spring contact terminatingin the terminal 26; through the barrier conducting portion II 0 toterminal 30; thence to post 28; through strap 3| to post 32; through thethermostatic bi-metal trip eminent` 45 to the post 33; thence throughstrap made up of Vparts 34, 35 and 36 to the'screw 31 and to arcuateshape strap 38 and screw 38'; and from these screws 3l and 38' to themembers 40, which have parts bearing against the bar 50; and from thisbar 50 through A the button 54 to the center terminal of the ctout. Theshell I2 of course, is in contact with the other terminal of the cut-outprovided by the shell thereof. In this manner a complete circuit throughthe device is furnished, which circuit will remain closed so long as thecurrent flow through the device is not of excess amperage.

When the parts are in this position the roller |00 is in the top of thediagonal slot 92 as shown in full lines in Fig. 4 and consequently thetarget |04 is positioned under the window |06. This target |04preferably will have some indicia to indicate amperage which the devicehas been designed to carry and at the same time this target may indicatethat the parts are in circuit closing position. P

Should the circuit become overloaded the thermostatic bi-metal trip 45,which is included in series in the circuit, will become actuated andwill so ex as to move the upstanding bar 49 of thelatch assembly from`the position shown in Fig. 8 to the position shown in Fig. 10, whereinit will be seen that this latch assembly has moved away from the primaryshutter an amount suiiicient for the latch 48 to clear the lug 90. Assoon as such clearance is provided the spring 68 forces the primaryshutter upwardly. As such upward movement progresses the rounded edgesof the dome-like parts 65 and 66 contact with the sloping cam surfaces25 of the two spring contacts forcing the terminals 26 and 30 carriedthereby simultaneously away in opposite directions from the conductingbarrier por- 5 tion I I0. At the same time`thewalls 62 and 64 of thisprimary shutter move upwardly to positions occupying the space formerlyoccupied by the terminals 26 and 30 on each side of the barrier I|0until finally these walls 62 and 64 have their upper ends engaging thelower ends of the sloping walls 'I2 and 'I3 of the secondary shutter.From this action it will be seen that the circuit is practicallyinstantaneously interrupted due to the forceful separation of theterminals 26 and 30 from the barrier |I0. As the primary shutter ismoved upwardly under the impetus of spring 68 the roller |00, whichrides in slot 92, causes the lever 98 to be moved from the full lineposition of Fig. 4 to the dotted line position of the same ligure.causes sliding of the telltale 94 until the target |05 is positionedbeneath the window |86. This target |05 may be colored, for example inred, to indicate that the parts of the circuit breaker have operated tointerrupt current flow therethrough.

Since upon inspection of the device, the telltale target indicates thatthe circuit has been interrupted, the entire device m'ay be removed fromthe cut-out, upon which movement the parts will automatically berestored to the normal position shown in Fig. 3. Such restoration isaccomplished by the expansion of spring 81 acting on the end of thecomposite bar through the secondary shutter 'I0' to force this bar andalso the primary shutter downwardly. The two terminals 26 and 30 restingagainst the walls 62 and 64 of the primary shutter are then engaged bythe walls 12 and I3 ofthe secondary shutter. The spring 8l is ofsuilcient strength to hold the primary and secondary shutters in contactagainst the'resiliency of the spring contacts carrying these terminals26 and 30. The downward movement continues until the lug 90 is againengaged by the latch 48 and until the proper target on the telltale hasbeen moved into visible position indicating the d evice has been reset.It is to be understood of course that the thermostatic bi-metal trip;once current flow has been interrupted, resumes its normal positionpermitting the latch 48 to be restored to normal position shown in Fig.v3. Thus the device is again in condition to be re-inserted into thecut-o-ut from which it has been removed or -it could be inserted in anyother suitable cut-out. Should it be inySerted in the same cut-out andthe overload continues the device will operate again in .the same mannerto interrupt the flow of current therethrough and a repetition of `thisprocedure will indicate clearly that some part of the apparatus Thismovement necessarily associated with the cut-out is shorted ormaterially overloaded. Consequently the device serves not only as aprotection for apparatus energized by the circuit including the same,but also serves eiiiciently as an indicatorof some fundamental error inthe circuit, all without the destruction of any part ofthe device.

In Figs. l1 to 14 inclusive, a modification has been illustrated. Thedevice so illustrated is adapted especially as a branch circuit breakerand a protective device for any individual appliance or group ofappliances' in a circuit which may otherwise be protected by a device ofa larger capaci- Y Vty. The operating parts of this modification aresubstantially similar to those previously described with a fewexceptions. Accordingly parts which are similar to those described inconnection with Figs. lto l inclusive have had the same referencecharacters applied thereto. The housing is composed of a portion theperiphery of which is not provided with threads but is of truly cy- Ylindrical form and also a portion ||5 forming a top for the housing. Thewindow |06 has been omitted but the top surface of the portion |I5 isprovided with two spaced openings'l20 disposed eccentrically and nearone edge thereof. These openings |20 are in register with two springcontact members |2| and |22 which are seated in cavities to provide ineffect sockets for the reception of the terminal prongs of an ordinarytwo-prong plug. These two contact members may be made in any desiredshape, one form being shown wherein the parts are of fragmentarytriangular configuration. The bases of the two contacts are secureddirectly to the annular internal surface I4'. One member |2| is fastenedto this surface by means of a conducting bar or rod |24 which extendsdownwardly through the wall of the portion to a conducting strap |25fastened in the bottom of the portion by some suitable arrangement.Strap |25 extends. to a connecting screw |26 which serves toelectrically connect the strap to an arm |21 of a contact prong |28which in turn extends downwardly through the bottom of the portion Thisprong |28 serves as one terminal of the device, being substituted forthe conducting shell |2 of the previous device.

The other contact |22 is secured together with a strap |29 to thesurface I4' by means of a headed overscrew |30, or by any other suitablearrangement. This strap |29 extends to a post II8 in the same manner asthe strap |1 previously described.y

A crank indicated generally at |3| has one arm portion |32 movable tocontact with the end of bar 50. The button 54 has been omitted from thisconstruction. The other arm |34 of the crank |3| is movable into aposition in parallelism with the prong |28 and this arm |34 serves asanother terminal prong whereby the device is in efiectprovided. with twocontact prongs similar to those of an ordinary plug. .A longheaded-screw member Y |35 passes through an opening in the portion l5into threaded engagement with an aperture in the portion so that yopenings |20 can be accurately brought into alignment with the 'contacts|2I and :|22 when the casing is assembled. The remaining parts of thedevice are similar to those previously described with the exception thatthe telltale 94 and the operating parts associated therewith have beenomitted.

The operation and use of this modified form of the invention issubstantially as follows: the

-ring 206 of similar insulating material.

two prongs |28 and |34 can be introduced into a proper receptacle by somoving the crank |3| into a position shown in dotted line in Fig. 12.

'When this movement has been accomplished the bar 50 will necessarily beforced upwardly relative to the housing, which movement causes thespring terminal members within the housing to be brought into contactwith the conducting barrier therein in the same manner as thatpreviously described. However current cannot flow through the deviceuntil a lug associated with some appliance has had its prongs insertedinto the openings |20 andthereby into contact with the members |2| and|22. Under these conditions a circuit may be traced from the prong |28through arm |21 to the strap |25; thence to the connecting rod |24 andto the contact |2|. From this contact |2| current flows through theappliance and to the contact |22, after which the circuit continuesthrough the operating parts of the circuit breaker tothe bar 50 andthence to prong |34 completing the Icircuit. Should the circuit becomeoverloaded the trip mechanism operates in the same manner as previouslydescribed, in turn interrupting the flow of current from one springterminal toanother through the conducting barrier. When the device hasbeen operated to interrupt current iiow the same can be automaticallyreset by removing the entire device from its receptacle, as a result ofwhich a spring 81 (not shown but similar to that of preceding figures)will force the composite bar terminating in the part 50 to the full lineposition of Fig. 12 thereby restoring lall of the parts to their initialposition. The device can then be re-inserted in its receptacle and theoperation thereof carried out in the ysame cycle.

It is to be understood of course, that a branch circuit breaker of thischaracter can be constructed in such form as to permit it to be engagedin an ordinary screw threaded receptacle instead of a receptacle for theaccommodation of parallel prongs. In this ,event the housingconstruction shown in Figs. l to may be used with the threaded shell onthe bottom of the housing. The only change would be the provision of twomembers 2| and |22 with the member |2| connected electrically to themetallic threaded shell instead of having this shell electricallyconnected directly to the post I8.

In Figs. to 1'7 inclusive the invention has been illustrated as beingembodied 'in a structure similar in configuration to the well knowncartridge fuses. In these figures 200 represents a tubular shell of somesuitable insulating material such as fibre, phenol condensation, etc.One end of the tubular shell 200 is of reduced external size as shown atfor the reception of a me-y tallic cap 202 permanently fastened theretoin some suitable manner. The other end of the shell also has a portionof reduced external diameter 204 on which is slidably mounted a metalliccap 20|5.l

Permanently secured within the shell 200 is a A member 201 of some goodconducting spring material `/has a U-portion 200 fastened to the ring206 by a rivet 209. One end of this member 201 is bent outwardly asshown at `2|0 and passes through a slot in the shell 200 to engage theKap 205i The other end of the member 201 is shaped as shown, beingprovided with a cam surface 2| A terminal 2|2 is fastened to the end ofthis member 201.

A second member 2|4 also of some conducting inner Wall of the shell 200in a manner not shown and is connected to one end of a U-shapedthermostatic bi-metal trip 220, similar to the trip member45k in theother embodiments. The two ends of this member 220 may be secureddirectly to the inner Wall of shell 200 and one end thereof is connectedby a conductor 22| to the metallic cap 202. Naturally this connection isfrom the opposite end of the member 220 from that to which the strap 2|6is connected.

A composite rod is secured within the complete assembly; such rod beingcomposed of a metallic rod 225 imbedded in an insulating connector 226,which also has imbedded therein a metallic rod 221, and finally asecondary shutter indicated generally at 228. This secondary shutter ismade up of a top 229, sidewalls 230 and tapering crosswalls 23|. Thissecondary shutter is permanently secured to an end of this bar 221. Oneend of the bar 225 ls permanently fastened to the slidable cap 205.- Acoil spring 232 is interposed between the bottom of the cap 202 andthetop of the secondary shutter 229, which shutter is composed entirely ofsome suitable insulating material. l

This modification also makes use of a. primary shutter likewise composedof some suitable inf sulating material and comprising parallel sidewalls234 and 235 and cross-walls 236. These cross-walls are hollowed out .toform a cavity 231 within which is mounted a coiled spring 238, one endof which bears against the top of the insulating connector 226. Thesidewall 235 of this shutter is provided with a lug-like extension 239,which extension is provided with a tapered side edge. v Y

Secured to the top of ring 206 by a screw 240 is a part of a latch at24| and including a. latch 242 and an upward extension 244 whichnormally lies adjacent the lower end or loop of the 'Ihe primary shutteris capable of axial movement relative to the bar or rod 221.

If desired the device shown in Figs. 15 to 17 can also be provided withment for indicating the condition of the operating parts. Sucharrangement has been shown in Fig. 17 wherein the casing 200 is providedwith a window 250 lled with some transparent material and the primaryshutter is provided with an extension 25| i on 'the surface of which aremounted some indicia 252 and 254. 'I'he indicia 252 and 254 will bemoved into alignment with the window 250 at different stages in theoperation of the device.

The operation of this device is substantially as follows: Fig. 15illustrates the position of the parts prior vto insertion of the same inclip terminals of the type commonly associated with cartridge fuses.This position may be called the' normal position of the cartridge. Aswill be seengfrom an inspection of this figure the two terminals 2|2 and2|,9 are held in` spaced relation and insulated from a'barrier portion250 of the bar 221 by the secondary shutter. The de-` vice may beinserted into' the proper clip terminals of a cut-out 'by firstinserting the cap 205 in one of the clip terminals, forcing the shell200 toward the end of this cap until it assumes the assembly indicatedgenerally 4U-shaped member 220. s

some telltale arrangel movement ofy the parts of the device, thecomposite bar within the casing has been moved until one end thereof iscloser to the end of cap 202 than in normal position thereby compressingspring 232. At the same time the secondary shutter 228 has been movedout of the path of movement of terminals 2| 2 and 2|9 permitting theseterminals, due to the resiliency of members 201 and 2'|4, to come intocontact with the barrier part 250 of bar 221. 'I'his bar naturally is ofsome good conducting material. The primary shutter is restrained frommovement due to the interengagenient between the latch 242 and the lug239. In this circuit-closed position (Fig. 16) a circuit is completedthrough the device from one clip terminal to the other of the cut-out.This circuit may be traced as follows: from the clip terminal holdingcap 205 to this cap 205; from cap 205 to end 2|0 of memberv 201; throughthis member 201 to terminal 2|2 then through barrier portion 250 toterminal 2|9; from terminal 2|9 through member 2|4 to conducting strap2|6 and thence Ito4 one end of the' U-shaped thermostatic bi-metal trip220; through this member 220 to the conductor 22| electricallyconnectedto the cap 202 and from this cap to the other clip terminal.

Since all current flowing through the device must necessarily flowthrough the U-shaped member 220 and since this member will be dee signedto flex upon a predetermined overload. it follows that should suchoverload occur this member is flexed in such fashion that the loop partthereof'moves toward the wall of the housing forcibly moving theupstanding part 244 along with it until the latch 242 clears the lug 239thereby releasing the primary shutter from its restraint. As soon assuch release occurs the spring 238 forces the primary shutter toward thesecondary shutter thereby causing the cam sur-4 faces at the tops of thewalls 236 to engage the cam surfaces 2|| and 2|8l forcing the twoterminals 2| 2 and 2|9 simultaneously out of contact and in oppositedirections with the barrier part 250. As this primary shutter continuesits movement toward the secondary shutter, through the impetus of spring238, the cross-walls ilnally become interposed between the barrier part250 and th terminals 2| 2 and 2|9. This operation naturally interruptsdevice. v

The device can be restored automatically to normal position by simplyremoving it from the the circuit through the clip terminals of thecut-out; upon which movement the spring 232 expands acting against thehead of the secondary shutter 228 to force the composite bar away fromcap 202, until this bar and the movable cap 205 together with alloperating parts assume the normal position of, Fig. l5. The device,having been reset, can be inserted in a cut-out in the same fashion asbefore described.

During the use of the device the telltale arrangement shown in Fig. 17may also be used. For example while the primary shutter is locked innormal position by the latch 242 the indicating portion 252 of thetelltale will be in alignment with the window 250. This portion 252 mayhave some indication thereon as to the amperage for which thefuse hasIbeen designed, or may be colored in some suitable fashion to indicatethat the device is in condition to permit the closing of the circuittherethrough. When the primary shutter has been released by the actionof the trip 220 upon an overload or a short the portion 254 of thetelltale is automatically moved into alignment with the window 250. Thisportion 254 may be colored red or may have some indication thereon tomake readily apparent that the parts have operated to interrupt currentflow.

In Figs. 18 and 19 a modied form of trip arrangement has been shown,which modiiication is particularly adaptable to use in connection withthe formsl of the invention shown in Figs. 1 to 14 inclusive. In thesefigures 260 represents a surace corresponding to the surface I4. To thissurface are secured two Z-shaped brackets 26l and 2&2 together withconducting straps 254 and 2%, which latter straps correspond to thestraps 536i and Ztl respectively. Use is made of a thermostatic bimetaltrip member composed of legs' 2t@ and 26.1 and a loop portion 26B.joining these legs. The upper ends of the legs are bent over and rivetedor otherwise secured to the tops of the two brackets 26H and 262.

The loop part 268 or the trip member is provided with an aperture inwhich is fitted a bushing 259. An Il -shaped leaf spring 210 is bent asshown in Fig. i8 and is held in proper assembly with the trip by meansof a screw 2li passing through an opening near the top of the springinto threaded engagement with an opening in the leg 266; and by a headedtrip member 212 which passes through an opening near the bottom of thespring 210 and through the bushing 269. A second leaf spring 214 has oneend riveted or otherwise secured to the leg 261 as indicated at 215while the other end bears against the head of the member 212.` Thisspring 214 of necessity is arranged in angular relation to the leg 261.

The use and operation of this arrangement is substantially as follows:as will be apparent from the drawings the end of member 212 extendsbeyond the bushing 269 and lies in the path of movement of a part of theprimary shutter and normally will engage a lug 216 thereon, which lugcorresponds to lug previously described. In some instances it may bedesirable to adjust the trip mechanism during the assembly thereof sothat the device will operate to interrupt current ow upon apredetermined overload. To this end the screw 21| may be adjusted toforce the upper end thereof closer to or further from the leg 266. Sincethis member 210 has a bent portion 211 resting against the leg, themember is in effect fulcrumed along the line of this portion 211 so thatmovement of the top part thereof causes movement of thabottom partthereof forcing the member 212 outwardly against the resilience ofspring 214 or inwardly. Thus the length of the part of member 212 inengagement with the lug 216 can be accurately predetermined .v

so that the degree of flexing of the bimetal release member can beproperly gauged to cause a release of the primary shutter at anycondition of overload for which the device may be designed.

The hereinbefore described method of interruption of a circuit possessesthe advantages that such interruptlon`can be accomplished substantiallywithout any destructive arcing between the moving parts. In practice ithas been found that this method, which embodies the Ystep of moving twoterminals simultaneously at the same rate of movementaway from aconducting barrier, serves to prevent such arcing. While the desiredmovement has been shown and described as being effected by a shutterwhich forcibly moves these terminals away from the barrier, it is to beunderstood that other arrangements for accomplishing such movement canbe employed. For example, springs may be utilized for moving theterminals away from the opposite sides of the barrier, in which event arelease mechanism would be employed in connection with the springs andin which embodiment it would be necessary for the springsv to havesubstantially the same tension. It is essential that the two terminalsbe moved out of' contact with the opposite sides of the conductingbarrier simultaneously, since movement of one terminal prior to movementof the other will cause destructive arcing. The shutter arrangementsdisclosed herein constitute the preferred form of actuating mechanismfor accomplishing these purposes since the wall which engages theterminals or members carrying the terminals can be symmetrically andaccurately shaped so that simultaneous departure of the terminals fromthe barrier can be assured.

Moreover the shutter arrangements shown pos- Sess the advantages in thatthey provide chambers which are of insulating material to isolate ortotally enclose each terminal so that these terminals are walled in andthereby arcing paths are eliminated and the paths for the flow ofcurrent to cause destructive arcing are so tortuous as to, underordinary circumstances, completely eliminate such arcing. The primaryshutter, since it is moved with great rapidity by its actuating springserves to quench any arc which might start under severe conditionsbefore such arc can reach the destructive stage. The U- shaped hoodmember described with the first two embodimentsof the invention providea top for the isolation chambers in which the terminals are locatedafter current interruption. The secondary shutter which is interposedbetween the terminals during resetting of the device assures that theseterminals cannot be moved to circuit-closing position until the devicehas been properly inserted in the cut-out designed to receive the same.

A further change may be made in the device "whereby the sliding contactbetween the bar 50 and the members 40 to assure good electric contactcan be replaced by a flexible conductor connected to the bar 50 and alsoconnected to some suitable point in the circuit. Such arrangement maysimplify the construction to some extent.

If desired means may be provided for manually tripping the device sothat the flow of current can be controlled for test or other purposes.To this end aI lever may be provided in any of the arrangementsshown,such lever being so mounted as to extend through the casing of anyarrangement and also being so mounted that manipulation of they leverwill cause release of the latch from the shutter to interrupt currentflow.

It is to be understood that the principles of l the present inventioncan be employed in devices other than those operating automatically uponan overload. Manually operated switches and other switches may be soconstructed as to ern- .body the salient features of the presentinvention. Accordingly the device is capable of modification beyond theillustrated embodiments and any limitations imposed thereupon are to beonly those defined by the following claims. p What is claimed is:

1. A device of the character described comprising a casing` forinsertion in a cut-out,'a' conducting member in said casing. a pair ofmovable .contact terminals in said casing, insulating means forinitially insulating said contact ter- CII minals from said conductingmember, said means being movable, upon insertion of said device into v acut-out, out of the path of said contact terminal whereby said contactterminals engage opposite sides of said conducting member to close acircuit through said device, and means operable upon overload for movingsaid contact terminals simultaneously in opposite directions from saidconductingl member to interrupt the circuit through said device.

2. A device of the character described comprising a casing for insertionin a cut-out, a conducting member in said casing, a pair of movablecontact terminals in said casing, insulating means for initially-insulating said contact terminals from said conducting member, saidmeans being movable, upon insertion of said device into a cutout, voutof the path of said contact terminals whereby said contact terminalsengage opposite sides of said conducting member to close a circuitthrough said device, means operable upon overload for moving saidcontact terminals simultaneously in opposite directions from saidconducting member to interrupt the circuit through said device, and aninsulating shutter movable simultaneously into position between saidcontact terminals and said conducting member,

3. A circuit breaker so constructed and arranged as to cooperate with acut-out, said circuit breaker comprising a casing, a conducting memberin said casing, a pair of movable contact terminals in said casing,insulating means for initially insulating said Contact terminals fromsaid conducting member, said means being movable, upon insertion of saiddevice into a cut-out, out of the path of said contact terminals wherebysaid contact terminals engage opposite sides of said conducting memberto close a circuit through saiddevice, means operable upon overload formoving said contact terminals simultaneously in opposite directions fromsaid conducting member to interrupt the circuit through said device, andmeans operable upon withdrawal of said device from a cut-out after acircuit interruption for restoring the parts thereof to initialposition.

4. vA circuit breaker so constructed and arranged as to cooperate with acut-out, said circuit breaker comprising a casing, a conducting memberin said casing, a pair of movable contact terminals in said casing,insulating means for initially insulating said contact terminals fromsaid conducting member, said means being movable, upon insertion of saiddevice into a cut-out, out of the path of said contact terminals wherebysaid contact terminals engage opposite sides of said conducting memberto close a circuit through said device, means operable upon overload formoving said contact terminals simultaneously in opposite directions fromsaid conducting member to interrupt the circuit through said device, aninsulating shutter movable simultaneously into position between saidcontact terminals and said conducting member, and means operable uponwithdrawal of said device from a cut-out after a circuit interruptionfor restoring the parts thereof to initial position. n

5. A device of the character described comprising a casing for insertionin a cut-out, a conducting member movably mounted in said casing,contact terminals movable into and out of contact with opposite sides ofsaid conducting member, a secondary shutter of insulating materialsecured to said conducting member for movement therewith, said secondaryshutter being initially in position .separating said contactterminalsfrom said conducting member, said conducting member, contactterminals and secondary shutter being movable upon insertion of saiddevice into a cut-out, into positions wherein said contact terminalsengage said conducting member to complete a circuit through said device,and a primary shutter of insulating material movable, upon a circuitoverload, to force said contact terminals simultaneously away from saidconducting member and to interpose parts of said primary shutter betweensaid contact terminals and said conducting member.

6. A device of the character described comprising a casing for insertionin a cut-out, a conducting member movably mounted in said casing,contact terminals movable into and out of contact with opposite sides ofsaid conducting member, a secondary shutter of insulating materialsecured to said conducting member for movement therewith, said secondaryshutter being initially in position separating said contact terminalsfrom said conducting member, said conducting member, contact terminalsand secondary shutter being movable upon insertion of said device into acut-out, into position wherein said contact ter-- minals engage saidconducting member to complete a circuit through said device, and aprimary shutter of insulating material movable upon a circuit overload,to force said contact terminals simultaneously away from said conductingmember and to interpose parts of said primary shutter between saidcontact terminals and said conducting member, said conducting memberbeing movable, upon removal of said device from a cutout after a circuitinterruption, to restore all oi' the parts of said device to initialpositions.

'7. A device of the character described comprising a casing forinsertion in a cut-out, a conducting member movably mounted in saidcasing, contact terminals movable into and out of contact with oppositesides of said conducting member, a secondary shutter of insulatingmaterial secured to said conducting member for movement therewith, saidsecondary shutter being initially in position separating said contactterminals from said conducting member, an external terminal for saiddevice, said external terminal being connected to and insulated fromsaid conducting member whereby movement of said external terminal causedby insertion of said device into a cut-out causes movement of saidconducting member and said secondary shutter into positions wherein saidcontact terminals engage said conducting member to complete a circuitthrough said device, and a primary shutter of insulating material mvableupon a circuit overload, to force said contact terminals simultaneouslyaway from said conducting member and tov interpose parts of said primaryshutter between said contact terminals and said conducting member.

8. A device of the character described oomprising a casing for insertionin a. cut-out, a conducting member movably mounted in said casing,contact terminals movable into and out of contact with opposite sides ofsaid conducting memberL a secondary shutter of insulating materialsecu-red to said conducting member for movement therewith, saidsecondary shutter being initiallyin position separating said contactterminals from said conducting member, said conducting member, contactterminals, and secondary shutter being movable upon insertion of saiddevice into a cut-out, into positions wherein said contact terminalsengage said conducting member to complete a circuit through said device,a

primary shutter of insulating material movable upon a circuit overload,to force said contact terminals simultaneous-ly away from saidconducting member and to interpose parts of said primary shutter betweensaid contact terminals and said conducting member, and a hood ofinsulating material cooperating with said shutters to form isolationchambers for said contact terminals.

,9. A device of the character described comprising a housing, acomposite bar slidable within said housing and having a conductingportion therein, a second conducting .portion of said bar extendingthrough said housing and being insulated from the first conductingportion, a pair of contact terminals movable into and out of contactwith opposite sides of said rst conducting portion, a shutter ofinsulating material secured to said bar for movement simultaneouslytherewith in one direction and for independent movement in the otherdirection, said shutter being normally restrained against independentmovement, means operable upon a predetermined overload for releasingsaid shutter for independent movement to cause simultaneous movement ofsaid contact terminals away from said conducting portion and for causinginterposition of part of said shutter between said contact terminals andsaid' conducting portion, said second mentioned conducting portionserving as one external terminal for said device and a second terminalsecured to the exterior of said device whereby said device can beinserted in a receptacle.

10. A device of the character described comprising a housing, acomposite bar slidable within said housing and having a conductingportion therein, a second conducting portion of said bar extendingthrough said housing and being insulated from the first conductingportion, a pair of -contact terminals movable into and out of contactwith opposite sides of said rst conducting portion, a shutter ofinsulating material secured to said bar for movement simultaneouslytherewith in one direction and for independent movement in the otherdirection, said shutter being normally restrained against independentmovement, means operable upon a predetermined overload for releasingsaid shutter for independent movement to cause simultaneous movement ofsaidcontact terminals away from said conducting portion and for causinginterposition of part of said shutter between said contact terminals andsaid conducting portion, a pair of external contact prongs for Asaiddevice, one of said prongs being pivotally-mounted to engage said secondconducting portion, and a pair of socket terminals in said housing toreceive the contact prongs of a plug.

11. A device ,of the character described comprising a substantiallytubular housing, a cap of conducting material rigidly secured to one endthereof, a second cap of conducting material slidably secured to theother end thereof, a conducting member within said housing, a pair ofcontact terminals mounted for movement into and out of contact withopposite sides of said conducting member and a shutter of insulatingmaterial slidably secured to said conducting member and means operableupon a predeter' mined overload for introducing a part of said shutterbetween said terminal members and said conducting member and for movingsaid contact terminals simultaneously away from said conducting memberto interrupt current flow, said caps being connected through saidcontact members whereby a circuit is completed when said contact membersare in contact with said conducting member.

l2. A circuit breaker so constructed and arranged as to cooperate with acutout, said circuit breaker having a conducting member and a pair ofterminals therein, said terminals being movable, upon engagement of saidcircuit breaker in said cut-out, into position engaging said conductingmember to complete a circuit through said 'circuit breaker, and meansoperable upon overload for moving said terminals simultaneously inopposite directions out of Contact with said conducting member.

13. A circuit breaker so constructed and arranged as to cooperate with acutout, said circuit breaker having a conducting member and a pair ofterminals therein, said terminals being movable, upon engagement of saidcircuit breaker in said cut-out, into position engaging said conductingmember to complete a circuit through said circuit breaker, and meansoperable upon overload for moving said terminals simultaneously inopposite directions out of contact with said conducting member whilesaid conducting member is maintained stationary.

14. A circuit breaker so constructed and arranged as to cooperatewith acutout, said .circuit breaker having a conducting member and a pair ofterminals therein, said terminals being movable, upon engagement of saidcircuit breaker in said cut-out, into position engagingsaid conductingmember to complete a circuit through said circuit breaker, meansoperable upon overload for moving said terminals simultaneously.

in opposite directions out of contact with said conducting member, and ashutter of insulating material movable simultaneously into positionbetween said terminals and said conducting member.

15. A circuit breaker so constructed and arranged as to cooperate with acutout, said circuit breaker having a conducting member and a pair ofterminals therein, said terminals being movable, upon engagement of saidcircuit breaker in said cut-out, into position engaging said conductingmember to complete a circuit through said circuit breaker, meansoperable upon overload for moving said terminals simultaneously inopposite directions out of contact with said conducting member, ashutter of insulating material movable simultaneously into positionbetween said terminals and said conducting member, and wall members ofinsulating material cooperating with said shutter to form isolationchambers for said

